As long as the sun is around, you need sunglasses because the light exposure can seriously damage your eyes and this exposure can intensify in winter– especially from snow reflectivity.
It's important to purchase sunglasses all year long, since they offer protection against UVA, UVB and UVC sunrays. These also help protect the delicate tissue around the eye, which can cause premature lines and wrinkles.
Of course, you should do! Because sunglasses are not worn to deter the heat of the sun, sunglasses are worn to prevent the sun's glare from bothering your eyes.